scholarly journals The influence of soil moisture on threshold runoff generation processes in an alpine headwater catchment

2010 ◽  
Vol 7 (5) ◽  
pp. 8091-8124 ◽  
Author(s):  
D. Penna ◽  
H. J. Tromp-van Meerveld ◽  
A. Gobbi ◽  
M. Borga ◽  
G. Dalla Fontana
Keyword(s):  
Soil Moisture ◽  
Overland Flow ◽  
Riparian Zone ◽  
Temporal Dynamics ◽  
Runoff Generation ◽  
Antecedent Conditions ◽  
Antecedent Moisture ◽  
Dry Conditions ◽  
Strong Control ◽  
Headwater Catchment

Abstract. This study investigates the role of soil moisture on the threshold runoff response in a small headwater catchment in the Italian Alps that is characterised by steep hillslopes and a distinct riparian zone. This study focuses on: (i) the threshold soil moisture-runoff relationship and the influence of catchment topography on this relation; (ii) the temporal dynamics of soil moisture, streamflow and groundwater that characterize the catchment's response to rainfall during dry and wet periods; and (iii) the combined effect of antecedent wetness conditions and rainfall amount on hillslope and riparian runoff. Our results highlight the strong control exerted by soil moisture on runoff in this catchment: a sharp threshold exists in the relationship between soil water content and runoff coefficient, streamflow, and hillslope-averaged depth to water table. Low runoff ratios were related to the response of the riparian zone, which was always close to saturation. High runoff ratios occurred during wet antecedent conditions, when the soil moisture threshold was exceeded. In these cases, subsurface flow was activated on hillslopes, which became major contributors to runoff. Antecedent wetness conditions also controlled the catchment's response time: during dry periods, streamflow reacted and peaked prior to hillslope soil moisture whereas during wet conditions the opposite occurred. This difference resulted in a hysteretic behaviour in the soil moisture-streamflow relationship. Finally, the influence of antecedent moisture conditions on runoff was also evident in the relation between cumulative rainfall and total stormflow. Small storms during dry conditions produced low runoff amounts, mainly from overland flow from the near saturated riparian zone. Conversely, for rainfall events during wet conditions, hillslopes contributed to streamflow and higher runoff values were observed.

scholarly journals The influence of soil moisture on threshold runoff generation processes in an alpine headwater catchment

2011 ◽  
Vol 15 (3) ◽  
pp. 689-702 ◽  
Author(s):  
D. Penna ◽  
H. J. Tromp-van Meerveld ◽  
A. Gobbi ◽  
M. Borga ◽  
G. Dalla Fontana
Keyword(s):  
Soil Moisture ◽  
Overland Flow ◽  
Riparian Zone ◽  
Temporal Dynamics ◽  
Runoff Generation ◽  
Antecedent Conditions ◽  
Antecedent Moisture ◽  
Dry Conditions ◽  
Strong Control ◽  
Headwater Catchment

Abstract. This study investigates the role of soil moisture on the threshold runoff response in a small headwater catchment in the Italian Alps that is characterised by steep hillslopes and a distinct riparian zone. This study focuses on: (i) the threshold soil moisture-runoff relationship and the influence of catchment topography on this relation; (ii) the temporal dynamics of soil moisture, streamflow and groundwater that characterize the catchment's response to rainfall during dry and wet periods; and (iii) the combined effect of antecedent wetness conditions and rainfall amount on hillslope and riparian runoff. Our results highlight the strong control exerted by soil moisture on runoff in this catchment: a sharp threshold exists in the relationship between soil water content and runoff coefficient, streamflow, and hillslope-averaged depth to water table. Low runoff ratios were likely related to the response of the riparian zone, which was almost always close to saturation. High runoff ratios occurred during wet antecedent conditions, when the soil moisture threshold was exceeded. In these cases, subsurface flow was activated on hillslopes, which became a major contributor to runoff. Antecedent wetness conditions also controlled the catchment's response time: during dry periods, streamflow reacted and peaked prior to hillslope soil moisture whereas during wet conditions the opposite occurred. This difference resulted in a hysteretic behaviour in the soil moisture-streamflow relationship. Finally, the influence of antecedent moisture conditions on runoff was also evident in the relation between cumulative rainfall and total stormflow. Small storms during dry conditions produced low stormflow amounts, likely mainly from overland flow from the near saturated riparian zone. Conversely, for rainfall events during wet conditions, higher stormflow values were observed and hillslopes must have contributed to streamflow.

scholarly journals Physically-based modelling of hydrological processes in a tropical headwater catchment (West Africa) – process representation and multi-criteria validation

2006 ◽  
Vol 10 (6) ◽  
pp. 829-847 ◽  
Author(s):  
S. Giertz ◽  
B. Diekkrüger ◽  
G. Steup
Keyword(s):  
Soil Moisture ◽  
Rainy Season ◽  
Overland Flow ◽  
Soil Layer ◽  
Hydrological Processes ◽  
Runoff Generation ◽  
Field Investigations ◽  
Physically Based ◽  
In The Beginning ◽  
Headwater Catchment

Abstract. The aim of the study was to test the applicability of a physically-based model to simulate the hydrological processes in a headwater catchment in Benin. Field investigations in the catchment have shown that lateral processes such as surface runoff and interflow are most important. Therefore, the 1-D SVAT-model SIMULAT was modified to a semi-distributed hillslope version (SIMULAT-H). Based on a good database, the model was evaluated in a multi-criteria validation using discharge, discharge components and soil moisture data. For the validation of discharge, good results were achieved for dry and wet years. The main differences were observable in the beginning of the rainy season. A comparison of the discharge components determined by hydro-chemical measurements with the simulation revealed that the model simulated the ratio of groundwater fluxes and fast runoff components correctly. For the validation of the discharge components of single events, larger differences were observable, which was partly caused by uncertainties in the precipitation data. The representation of the soil moisture dynamics by the model was good for the top soil layer. For deeper soil horizons, which are characterized by higher gravel content, the differences between simulated and measured soil moisture were larger. A good agreement of simulation results and field investigations was achieved for the runoff generation processes. Interflow is the predominant process on the upper and the middle slopes, while at the bottom of the hillslope groundwater recharge and – during the rainy season – saturated overland flow are important processes.

scholarly journals Physically-based modelling of hydrological processes in a tropical headwater catchment in Benin (West Africa) – process representation and multi-criteria validation

2006 ◽  
Vol 3 (2) ◽  
pp. 595-651 ◽  
Author(s):  
S. Giertz ◽  
B. Diekkrüger ◽  
G. Steup
Keyword(s):  
Soil Moisture ◽  
Rainy Season ◽  
Overland Flow ◽  
Soil Layer ◽  
Hydrological Processes ◽  
Runoff Generation ◽  
Field Investigations ◽  
Physically Based ◽  
In The Beginning ◽  
Headwater Catchment

Abstract. The aim of the study was to test the applicability of a physically-based model to simulate the hydrological processes in a headwater catchment in Benin. Field investigations in the catchment have shown that lateral processes as surface runoff and interflow are most important. Therefore the 1-D SVAT-model SIMULAT was modified to a hillslope version (SIMULAT-H). Due to a good database the model was evaluated in a multi-criteria validation using discharge, discharge components and spatially distributed soil moisture data. For the validation of discharge good results were achieved for dry and wet years. Main differences were observable in the beginning of the rainy season. The comparison of the discharge components determined by hydrochemical measurements with the simulation revealed that the model simulated the ratio of groundwater fluxes and fast runoff components correctly. For the validation of the discharge components of single events larger differences were observable, which was partly caused by uncertainties in the precipitation data. The representation of the soil moisture dynamics by the model was good for the top soil layer. For deeper soil horizons, which are characterized by higher gravel content, the differences between simulated and measured soil moisture were larger. Concerning the runoff generation processes a good agreement of simulation results and field investigations was achieved. On the upper and the middle slope interflow is the predominant process, while at the bottom of the hillslope groundwater recharge and – during the rainy season – saturated overland flow are important processes.

scholarly journals Multiple runoff processes and multiple thresholds control agricultural runoff generation

2016 ◽  
Vol 20 (11) ◽  
pp. 4525-4545 ◽  
Author(s):  
Shabnam Saffarpour ◽  
Andrew W. Western ◽  
Russell Adams ◽  
Jeffrey J. McDonnell
Keyword(s):  
Soil Moisture ◽  
Overland Flow ◽  
Riparian Zone ◽  
Hydrologic Response ◽  
Rainfall Runoff ◽  
Runoff Generation ◽  
Antecedent Soil Moisture ◽  
Rainfall Events ◽  
Major Ion ◽  
Multiple Thresholds

Abstract. Thresholds and hydrologic connectivity associated with runoff processes are a critical concept for understanding catchment hydrologic response at the event timescale. To date, most attention has focused on single runoff response types, and the role of multiple thresholds and flow path connectivities has not been made explicit. Here we first summarise existing knowledge on the interplay between thresholds, connectivity and runoff processes at the hillslope–small catchment scale into a single figure and use it in examining how runoff response and the catchment threshold response to rainfall affect a suite of runoff generation mechanisms in a small agricultural catchment. A 1.37 ha catchment in the Lang Lang River catchment, Victoria, Australia, was instrumented and hourly data of rainfall, runoff, shallow groundwater level and isotope water samples were collected. The rainfall, runoff and antecedent soil moisture data together with water levels at several shallow piezometers are used to identify runoff processes in the study site. We use isotope and major ion results to further support the findings of the hydrometric data. We analyse 60 rainfall events that produced 38 runoff events over two runoff seasons. Our results show that the catchment hydrologic response was typically controlled by the Antecedent Soil Moisture Index and rainfall characteristics. There was a strong seasonal effect in the antecedent moisture conditions that led to marked seasonal-scale changes in runoff response. Analysis of shallow well data revealed that streamflows early in the runoff season were dominated primarily by saturation excess overland flow from the riparian area. As the runoff season progressed, the catchment soil water storage increased and the hillslopes connected to the riparian area. The hillslopes transferred a significant amount of water to the riparian zone during and following events. Then, during a particularly wet period, this connectivity to the riparian zone, and ultimately to the stream, persisted between events for a period of 1 month. These findings are supported by isotope results which showed the dominance of pre-event water, together with significant contributions of event water early (rising limb and peak) in the event hydrograph. Based on a combination of various hydrometric analyses and some isotope and major ion data, we conclude that event runoff at this site is typically a combination of subsurface event flow and saturation excess overland flow. However, during high intensity rainfall events, flashy catchment flow was observed even though the soil moisture threshold for activation of subsurface flow was not exceeded. We hypothesise that this was due to the activation of infiltration excess overland flow and/or fast lateral flow through preferential pathways on the hillslope and saturation overland flow from the riparian zone.

scholarly journals Multiple runoff processes and multiple thresholds control agricultural runoff generation

2016 ◽  
Author(s):  
Shabnam Saffarpour ◽  
Andrew W. Western ◽  
Russell Adams ◽  
Jeffrey J. McDonnell
Keyword(s):  
Soil Moisture ◽  
Overland Flow ◽  
Riparian Zone ◽  
Agricultural Runoff ◽  
Seasonal Effect ◽  
Hydrologic Response ◽  
Runoff Generation ◽  
Rainfall Events ◽  
Riparian Area ◽  
Saturation Excess

Abstract. Hydrologic connectivity associated with runoff processes is a critical concept for understanding catchment hydrologic response at the event timescale. However, to date, most attention has focused on single runoff response types in individual research catchments. Here we examine how runoff response and the catchment threshold response to rainfall affect a suite of runoff generation mechanisms in a small agricultural catchment. A 1.37 ha hillslope in the Lang Lang River catchment, Victoria, Australia was instrumented and hourly data of rainfall, runoff, shallow groundwater level and isotope water samples were collected. We analyse 60 rainfall events that produced 38 runoff events over two runoff seasons. Our results show that the catchment hydrologic response was typically controlled by the antecedent soil moisture condition and rainfall characteristics. There was a strong seasonal effect in the antecedent moisture conditions that led to marked seasonal scale changes in runoff response. Analysis of shallow well data revealed that streamflows early in the runoff season were dominated primarily by saturation excess overland flow from the riparian area. As the runoff season progressed, the catchment soil water storage increased and the hillslope connected to the riparian area. The hillslope transferred a significant amount of water to the riparian zone during and following events. Then, during a particularly wet period, this connectivity to the riparian zone, and ultimately to the stream, persisted between events for a period of one month. These findings are supported by isotope results which showed the dominance of pre-event water, and increased contributions of new water early (rising limb and peak) in the event hydrograph for wetter conditions. We conclude that event runoff at this site is a combination of subsurface event flow and saturation excess overland flow. However, during high intensity rainfall events, flashy hillslope flow was observed even though the soil moisture threshold for activation of subsurface flow was not exceeded. We hypothesize that this was due to the activation of infiltration excess overland flow and/or fast lateral flow through preferential pathways on the hillslope and saturation overland flow from the riparian zone.

Dominant drivers of runoff in a slash-and-burn affected catchment in upland Eastern Madagascar

2021 ◽  
Author(s):  
Bob W. Zwartendijk ◽  
H.J. (Ilja) van Meerveld ◽  
Ryan J. Teuling ◽  
Chandra P. Ghimire ◽  
L. Adrian Bruijnzeel
Keyword(s):  
Soil Moisture ◽  
Overland Flow ◽  
Quantitative Information ◽  
Forest Loss ◽  
Runoff Generation ◽  
Catchment Scale ◽  
Valley Bottom ◽  
Antecedent Soil Moisture ◽  
Slash And Burn ◽  
Slash And Burn Agriculture

<p>In many tropical areas slash-and-burn agriculture is an important driver of forest loss. In areas where slash-and-burn agriculture has been practiced for decades, land cover is typically a mosaic of patches of remnant forest, fields under active cultivation, fallows in various stages of regrowth (ranging from young shrub to semi-mature), and degraded fire-climax grasslands. Although runoff generation mechanisms are expected to be different for these different patches, little quantitative information is available in this regard, particularly at the catchment scale and over longer time-scales (i.e., multiple slash-and-burn cycles).</p><p>We re-instrumented a 31 ha catchment in upland Eastern Madagascar, where slash-and-burn agriculture has been practiced for more than 70 years in 2015; it had been monitored between 1963 and 1972 as well<sup>1</sup>. We measured streamflow at two locations and overland flow and soil moisture for four hillside plots (0.05 – 1.93 ha): one plot under repeatedly coppiced and burned <em>Eucalyptus</em> and three plots under young shrub and tree fallows. One of the plots underwent rudimentary terracing in the past. We analysed the rainfall-runoff dynamics for 50 rainfall events (median 12 mm, maximum 71 mm).</p><p>For 60% of the events, the stormflow coefficient (minimum contributing area) was <3%, which is the proportion of valley-bottom wetlands and rice paddies in the catchment. Stable isotope sampling for five storm runoff events indicate a maximum total event-water contribution of 16%. However, instantaneous event-water contributions were as high as 66%. The hillside plot runoff response was dominated by saturation-excess overland flow and showed strong threshold behaviour in terms of the antecedent soil moisture storage in the upper 30 cm of the soil plus the event total rainfall amount (ASI + P). Average threshold values for overland flow occurrence ranged from 87 mm for the coppiced <em>Eucalyptus</em> to 137 mm for the young fallow plots (regardless of terrace presence). Stormflow also increased after an ASI+P-threshold was exceeded (100 mm based on the soil moisture sensors for the <em>Eucalyptus</em> plot and 150 mm for the sensors at the tree fallow plots).</p><p>These results indicate an increased hydrological connectivity between hillslopes and valley bottom under wetter conditions and that stormflow in the study catchment is strongly affected by variations in seasonal rainfall. The results will be used to validate a hydrological model to determine the net effect of concurrent changes in soil infiltrability and vegetation water use associated with forest loss and recovery on stormflow totals and the seasonal flow regime.</p><p><strong><sup>1</sup></strong>Bailly, C., de Coignac, G.B., Malvos, C., Ningre, J.M., and Sarrailh, J.M. (1974). Étude de l'influence du couvert naturel et de ses modifications á Madagascar. Expérimentations en bassins versants élémentaires. Cahiers Scientifiques, 4. Centre Scientifique Forestier Tropical, Nogent-sur-Marne, France, 114 pp.</p>

Effect of temporal rainfall distribution and soil type on soil moisture and runoff generation in semi-arid Zimbabwe

2007 ◽  
Vol 38 (3) ◽  
pp. 249-263 ◽  
Author(s):  
F.T. Mugabe ◽  
M.G. Hodnett ◽  
A. Senzanje
Keyword(s):  
Soil Moisture ◽  
Overland Flow ◽  
Daily Rainfall ◽  
Soil Surface ◽  
Runoff Generation ◽  
Stream Channels ◽  
Wet Season ◽  
Sodic Soils ◽  
Rainfall Distribution ◽  
Semi Arid

This paper examines the effect of temporal rainfall distribution on soil moisture and runoff generation in the 5.9 km2 Mutangi catchment in semi-arid Zimbabwe. Rainfall, soil moisture and runoff were measured during the 1999/00 and 2000/01 rainy seasons during which periods 755 mm and 615 mm of rainfall were received, respectively. The percentage of rainfall totals in these periods were 58% and 69%, respectively, in February. The total catchment runoff was 102 mm and 63 mm, of which 52% and 49% were recorded over 6 and 4 d in 2000 and 2001, respectively. Baseflow was negligible. Rainfall intensities were generally low. In the 1999/00 season there were 2 and 8 h with intensities >20 mm h−1 and 10 mm h−1, respectively. Some runoff appears to be generated by Hortonian overland flow (HOF), mainly in the early wet season before ploughing creates a rougher soil surface. The dominant process of runoff in this catchment was saturated overland flow (SOF), which occurs when the soils become saturated from below. The sodic soils along the stream channels appear to generate most of the runoff because of their small capacity to store water before saturation. The ridge soils are coarse sands, with a large capacity to store rainfall. The transitional (slope) soils have an intermediate capacity to store water. If there is a sequence of daily events that completely fills the storage available in both the sodic and transitional soils, and which begins to saturate the ridge soils, there could be very large amounts of runoff (>50% of the daily rainfall). The occurrence of such runoff events depends very heavily on the distribution of rainfall. Dry spells between rain events create storage, thereby reducing the risk of runoff from the next events.

A scheme for evaluating the effectiveness of riparian zones in reducing overland flow to streams

Soil Research ◽  
1998 ◽  
Vol 36 (4) ◽  
pp. 683 ◽  
Author(s):  
N. F. Herron ◽  
P. B. Hairsine
Keyword(s):  
Overland Flow ◽  
Riparian Zone ◽  
Good Condition ◽  
Infiltration Rate ◽  
Subsurface Water ◽  
Riparian Zones ◽  
Riparian Areas ◽  
Management Scenarios ◽  
Antecedent Moisture ◽  
Water Redistribution

Two time-independent equations are developed to assess the effectiveness of riparian zones in reducing overland flow to streams for events in which the time-scale of subsurface water redistribution exceeds that of the rainfall event. In one equation, the effectiveness of the riparian area is limited by the storage capacity of its soils, while in the other equation, the infiltration rate determines the buffer’s effectiveness. Riparian zone widths, expressed as a proportion of total hillslope length, are calculated for a number of different climate, antecedent moisture, and management scenarios for hillslopes of varying topographic convergence. A riparian zone width not exceeding 20% of total hillslope length is proposed as a practical management option in this paper. Riparian zone widths that fall within these bounds are predicted for areas where both the hillslopes and riparian areas are in good condition. Where conditions in either area are degraded, disproportionately large riparian buffer widths are predicted. The results suggest that land management initiatives need to be directed at the catchment as a whole if riparian buffers of realistic widths are to be effective.

Which event produces the largest flash flood? Considering rainfall characteristics, initial soil moisture, retention and run-on infiltration

2020 ◽  
Author(s):  
Markus Weiler ◽  
Hannes Leistert ◽  
Andreas Steinbrich
Keyword(s):  
Soil Moisture ◽  
Return Period ◽  
Overland Flow ◽  
Flash Flood ◽  
Joint Probability ◽  
Flash Floods ◽  
Runoff Generation ◽  
Runoff Formation ◽  
Initial Soil Moisture ◽  
Initial Soil

<p>Local heavy precipitation regularly causes great damage resulting from flash floods in small catchments. Appropriate discharge records are usually unavailable to derive an extreme value statistics and regionalization approaches predicting peak discharge from discharge records of larger basins cannot consider the small-scale effects and local processes. In addition, forecasting flash floods from rainfall forecast requires to identify the event conditions under which a catchment is most prone to trigger flash floods. Therefore, factors influencing runoff formation and concentration need to be identified based on catchment characteristics in order to predict flood hydrographs, geomorphic processes and flood inundation.</p><p>We have developed a framework depending on the joint probability of soil moisture and rainfall and used the distributed, processed-based rainfall-runoff model RoGeR to predict the spatial explicit probability of soil moisture and linking this to overland-flow and subsurface flow generation assuming different scenarios of soil moisture and rainfall characteristics. Selected combinations result in a joint probability with a specified return period (e.g. 100 year), but are based on different probabilities for rainfall amount, duration and initial soil moisture. From this, the combination of a precipitation event and initial soil moisture condition can be determined which generates the largest runoff generation. In addition, we found, that accounting for the spatially and temporally controlled superimposition of runoff formation and runoff concentration, including the possible infiltration of overland flow (run-on infiltration) along the flow path and the retention in depression can have considerable influence on modelled peak discharge and discharge volume for a given catchment. For this purpose, various methods were developed and tested considering the effects of run-on infiltration and retention, from complex 2D hydraulic models coupled with RoGeR to simpler approaches considering run-on infiltration only locally or based on the difference between actual and potential infiltration. These approaches were tested in different catchments with different soils, geologies and land use. Also, the sensitiviy of surface roughness was considered.</p><p>We developed an interactive spatial explicit method, which combines the joint probability of soil moisture and rainfall for runoff formation with hydraulic assumptions to determine runoff concentration and thus the corresponding design hydrographs and the specific conditions a catchment can trigger flash floods. This information can on the one side help to generate flash flood risk maps, but should also be considered in order to provide adequate catchment specific information for heavy precipitation risk management. We could clearly demonstrate that only the combined consideration of factors affecting flood formation and concentration and its implementation into a statistical framework allows to predict floods for a specific return period (which is not equal to the return period of precipitation) for small catchments where different runoff generation mechanisms occur simultaneously.</p>

scholarly journals Use of deuterium to understand runoff generation in a headwater catchment containing a dambo

1998 ◽  
Vol 2 (1) ◽  
pp. 65-76 ◽  
Author(s):  
M. P. McCartney ◽  
C. Neal ◽  
M. Neal
Keyword(s):  
Overland Flow ◽  
Hydrological Cycle ◽  
Hydrograph Separation ◽  
Runoff Generation ◽  
Rainfall Characteristics ◽  
Headwater Catchments ◽  
Antecedent Conditions ◽  
Storm Flow ◽  
Total Proportion ◽  
Made In

Abstract. Dambos, seasonally saturated wetlands, are widespread in headwater catchments in southern Africa and play an important role in the regional hydrological cycle. However, the processes influencing runoff from these catchments are poorly understood. This paper reports an isotopic investigation of runoff-generating mechanisms within a Zimbabwean catchment containing a dambo. Hydrograph separation using deuterium reveals that, once the dambo is saturated, up to 70% of total storm flow can be considered "new" water (i.e. derived directly from rainfall generating the runoff event). However, both the total proportion and the instantaneous maximum amount of "new" water in hydrographs are sensitive to rainfall characteristics and antecedent conditions. These results are (1) compatible with observations made in catchments in temperate climates when wetlands are present, and contrast with results obtained when wetlands are absent and (2) consistent with saturation overland flow, generated in saturated regions of the dambo, being the major storm runoff mechanism. To reconcile these observations with past perceptions that dambos attenuate flood flows, a dual role for dambos in storm flow production is postulated.

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